I suggest you ...

Make the Visual Studio installer more customizable

Let one don't install some components if one don't need it - for example Silverlight development support, visual designers for WPF or Windows Forkflow, or unit testing (many developers use third-party solutions like NUnit and don't use VS built-in testing tools).

I did a minimal install of Visual Studio 2015 64-bit Community RTM. It made only 15 entries in Windows installed "Programs and Features". 6 of them are different Visual C++ redistributables, 5 are .net framework things, 2 are CLR types for SQL server, 1 is help viewer and the other one is visual studio itself. The install size of Visual Studio 2015 is 3.57GB. All 14 other items combines to about 400MB. I think it is in good shape now in terms of installation custommization.

Per what I see in VS2015RC's installer, MS has ignored this request completely. There's no way to install only C++, at example:
http://puu.sh/iYECY/0c3a161e12.pngAnd 8GiB minimum install is ridiculous.

I assume VS team was more concentrated on some bells'n'whistles than on real improvements.

I'd like to remove all the components related to the archaic Visual Basic language. I use only C# and I would like to be able to install only the things related to it. It is very unlikely if one is using C# to mix it with Basic. Plus, SSD disk are kind of an expensive thing in order to play around with it in your way with 20G installation (Web, Windows Phone, Azure and iOS development). This is insane.

You know what guys? I abandoned VS. After what you'd ask? After being acquainted with VS2013, which installed over 11 gigs on my PC with minimal install. And installation process took about 3 hours, about a hour of which I saw ridiculous "preparing installation script". Now I'm happily developing on Lubuntu, with all tools I need installed with 'sudo apt-get install build-essential cmake git'. It usually takes 2-3 minutes to deploy all packages needed.

Keep up to make VS 30GiB! 11 is too small! You won't be able to compete with Star Citizen (about 100 gigs :)

You (Microsoft) should make the setup customizable. I need only VB.NET and C# in my case. I do not need C++/SQL Server/Windows Mobile Development etc. The only reason I am still using VS 2008 Express Editions is because the setup was customizable. I hope that the setup will get customizable in VS2015.

I have queried for the Win32_Product on a machine before and after installing Visual Studio 2013. The installer installs over 130 software packages! Many of these packages are entirely unnecessary for my day-to-day job or even my side projects. Some of these packages seem like typical shovelware, especially those related to Microsoft Advertising platforms, Windows Azure, or Windows Phone development. Trying to uninstall a package will typically lead to a very unstable IDE, otherwise I could probably uninstall over 100 packages.

You said in your comment "We are currently evaluating whether we will be able to include this into the product."? But you are evaluating this now for more than a year! Two things are very slow at Microsoft, the VS2013 installer and the decision.

Yes! Please make it more modular!
I have a VS2013 Ultimate license from my university, and I like some of the extra features, but most of them are useless to me. For example, I don't need Azure, Silverlight, Team Foundation, LightSwitch, and a lot of other components.
I have a laptop with a 70GB SSD, VS2013 needs about 10GB...

I was going to give a try to VS2013 community edition, but no thanks, a setup that has only 4 customization options and installs 10 GB of useless things just to get a C++ compiler and its IDE is definitely not what I'm looking for. Hard drives have might have limited space, SSDs on laptops even more. I'll come back when I'll be able to install just the IDE, the compiler, and the Win32 SDK.

Please please do not blow my system with 100500 components(extensions) that I never ever use, if I choose "Web Development" only, do not install Windows Phone Images and Hyper-V, or at least give us easy way to get rid of all this stuf

+3 for this "old new" feature.. as far as I can remember, this was present before VS2012, but magically it was probably sacrificed for "more important features".
Unfortunately it's typical Microsoft: the product gets worse and worse (slower, larger, less usable) by each release BUT we have "brand new skin" and such stuff, right? Wonder if I'm gonna be still alive when once STABILITY and performance will have more priority than "brand new skin" and supporting every possible trendy technology. It should be time to rethink the concepts.